Our prior microelectrode studies of red nucleus in trained monkeys define a relatively homogeneous population of promotor neurons. The majority of cells locatoed in the dorsomedial magnocellular region of red nucleus show dishcarge patterns tightly coupled to movement of the contralateral hand. We found large, directionally specific changes in discharge rate that precede each movement and are well correlated with the velocity and the duration of the movement. We now propose to use the RNm (magnocellular red nucleus) as a model system for studying the properties of descending motor control signals, and the manner in which the cerebellum participates in their genesis. Our specific aims during the coming grant period are: (1) To investigate the detailed motor map of the dorsomedial hand region of RNm, (2) to study the parametric dependence of RNm discharge on kinematic and kinetic movement parameters, (3) to explore the sensory relations of these neurons using quantitative methods and (4) to initiate correlative studies of the interpositus (IP) input to RNm. The results of these studies should be relevant to our understanding of movement disorders such